RCA RLDEDV3988-A Flickering Backlight

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  • neilc6
    Badcaps Legend
    • Nov 2015
    • 1550
    • Canada
    #1

    RCA RLDEDV3988-A Flickering Backlight

    The backlight LED's pulse on briefly every second. There is a previous thread about this problem with a confusing solution. This is an LED TV with a built in DVD player and combined power supply/main board. https://www.badcaps.net/forum/showth...t=rldedv3988-a

    The backlight power wires appear to be fed by 3 thin red wires. I measured about 25V DC steady on each of them. They were not pulsing. The last post on the previous thread indicates the cause could be bad LED's in the strip.

    There doesn't appear to be a DIM or ADJ signal since it is all one board. There also is no backlight control, just brightness in the user menu.

    Googling the number on the sticker of the board T390HVN01.0, I can find a datasheet for the panel.
    Attached Files
    Last edited by neilc6; 01-25-2017, 06:01 PM.
    Tags: None
    • neilc6
      Badcaps Legend
      • Nov 2015
      • 1550
      • Canada
      #2
      Re: RCA RLDEDV3988-A Flickering Backlight

      I disassembled the panel and found the top row of three 10-LED strings is out. Guess I need to research troubleshooting and fixing this.

        Comment

        • CapLeaker
          Leaking Member
          • Dec 2014
          • 7967
          • Canada
          #3
          Re: RCA RLDEDV3988-A Flickering Backlight

          those RCA's are utter garbage. Even on a Vestel set, one is able to adjust the back light in the menu. Also it's one of these one board has it all TV's.
          Anyway... test each LED on that bad sting with your DMM in diode mode.

            Comment

            • neilc6
              Badcaps Legend
              • Nov 2015
              • 1550
              • Canada
              #4
              Re: RCA RLDEDV3988-A Flickering Backlight

              When I took the LCD panel off and disconnected the LVDS connector, the backlights remain on but dimmer. This would be an easier way to diagnose this problem.

              I took a razor blade and scraped a bit of the soldermask off each side each LED to check each one and found one bad with the DMM. Luckily, I saved one strip of a LED of a broken screen TV that I can use for a repair.

                Comment

                • neilc6
                  Badcaps Legend
                  • Nov 2015
                  • 1550
                  • Canada
                  #5
                  Re: RCA RLDEDV3988-A Flickering Backlight

                  Good news, I fixed it by replacing the LED. Very difficult to solder on because of the narrow space between leads. Bad news, I cracked the LCD panel. I knew it was delicate and tried to be very careful but it cracked anyway. If anyone needs parts.... 2 LED strips, DVD drive, main board.....

                    Comment

                    • petehall347
                      Badcaps Legend
                      • Jan 2015
                      • 4422
                      • United Kingdom
                      #6
                      Re: RCA RLDEDV3988-A Flickering Backlight

                      oh shit .. only had a few apart and that always worries me . my hands shake so much i think it will break there and then .

                        Comment

                        • neilc6
                          Badcaps Legend
                          • Nov 2015
                          • 1550
                          • Canada
                          #7
                          Re: RCA RLDEDV3988-A Flickering Backlight

                          I've broken every panel I've had to disassemble. My mistake this time was I moved the panel with all the plastic panel pieces behind them. I thought this would protect it but ended up flexing it more instead. I also grabbed it by the sides which flexed it more- should have only grabbed it from the top. Once I had the front bezel off, the LCD could have been removed on it's own by prying off the circuit boards at the bottom that were double sided taped down. Initially I just flipped everything over to take a look at the backlights (panel was still fine) but decided to remove it to better access the strips. In hindsight, this was the correct approach to minimize handling and I should have just pried off the top LED strip.
                          Last edited by neilc6; 01-26-2017, 07:49 PM.

                            Comment

                            • JeffJ
                              Senior Member
                              • Apr 2012
                              • 189
                              • Canada
                              #8
                              Re: RCA RLDEDV3988-A Flickering Backlight

                              I've never broken a panel yet *knocks on wood* but i find when i'm stripping a tv for led strips because of a panel fault (thanks Samsung, so many...) I shake it and wobble it laugh at the sound it makes but it never cracks on me. Go figure. Not to say it didn't damage the tab bonds, because they already were bad but never cracked one. they seem overly robust when i have no care for them.

                              When i care for the panel, i'm almost a nervous wreck when i remove it and place it in a safe spot.

                                Comment

                                • CapLeaker
                                  Leaking Member
                                  • Dec 2014
                                  • 7967
                                  • Canada
                                  #9
                                  Re: RCA RLDEDV3988-A Flickering Backlight

                                  I haven't broken a panel yet either. But I guess there is always the risk one has to live with.

                                    Comment

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